1. Field of the invention
The present invention relates to single insert ball nose cutters used in the machine tool industry, and more particularly to a ball nose cutter having a circularly cross-sectioned cutter insert removably resident in a circularly curved holding groove of a cutter body. Still more particularly, the present invention relates to a ball nose cutter of the class aforesaid wherein the cutter insert has a pair of cutting tips, either one of which being selectable for service.
2. Description of the Prior Art
Indexable end milling cutting tools are well known in the art for use in a variety of machining operations. These cutting tools include a head portion having replaceable cutting edges of one or more predetermined rake angles for cutting, boring or otherwise contouring a workpiece. The other end of these cutting tools have a shank for removable connection with an end mill or other torque transmitting machine. The actual speed and contact relationship the cutting tool with the workpiece is ordinarily, but not necessarily, predetermined by computer numeric control (CNC) of the torque transmitting machine.
One type of indexable end milling cutting tool is a ball nose cutter. A first class of conventional ball nose cutter has a ball nose shaped cutter body of predetermined diameter. In a first form, the cutter body is constructed of a high speed steel or solid carbide material that is provided with one or more cutting edges of predetermined rake, wherein a gullet for chip removal is provided adjacent the one or more cutting edges. In a second form, which is improved over the first form, the cutting body is again of a ball nose shape and constructed of an alloy steel. The cutting body now has removably connected thereto a plurality of seated cutter inserts of generally rectangular shape, provided with one or more cutting edges, and constructed of brazed carbide, ceramic or other hardened material. Adjacent the cutter inserts, the cutter body is provided with one or more gullets for facilitating removal of chips from the workpiece. An example of the second form of ball nose cutter are models 16W1X and 16W1B of the Ingersoll Cutting Tool Company, Rockford, Ill. The aforesaid first class of ball nose cutter suffers from complicated, difficult and expensive processes to restore the ball nose cutter specification whenever the cutting edges thereof have become dulled from use.
Accordingly a second class of conventional ball nose cutter has been developed in the prior art in which a single circular cross-sectioned cutter insert is removably seated in a fiat holding groove of a ball nose shaped cutter body, wherein a screw is transversely secured with respect to the cutter body for holding the cutter insert in a seated relationship with respect to the flat holding groove. A cutting edge is provided on opposite sides of the cutting insert, and a gash is provided on each side of the cutter insert at the centerline of the ball nose cutter. Each gash provides a selectable cutting point of sorts for promoting neat, curled chips from the workpiece. An example of this second class of ball nose cutter is produced by Walter Kieninger Co. of Lahr, Germany, and represented in the U.S.A. by Dapra Corporation of Bloomfield, Conn. The aforesaid second class of ball nose cutter suffers from the absence of a true cutting tip. The "gash" is a poor substitute therefor, but is provided because of the symmetry necessary to make the cutter insert reversible with respect to the flat holding groove.
Accordingly, what is needed is a ball nose cutter having a replaceable single cutter insert in which the cutting edge includes at least one true cutting tip.